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31.
快速Hartley变换(FHT)是离散Hartley变换(DHT)的快速算法,它是一种实序的变换,其正反变换具有完全相同的形式。利用FHT进行实数据相关可以避免复数运算,特别适用于采和可编程数字信号处理器(DSP)来实现的实时相关器。和FFT相关算法相比,在保持同样数据吞吐率的情况下,采用FHT方法,可显著减少系统所需的高速存贮器,从而,可降低系统的成本。本文讨论了DHT的有关性质和FHT算法和运 相似文献
32.
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Masahito Matsubayashi Takashi Hibiki Kaichiro Mishima Koji Yoshii Koji Okamoto 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2003,510(3):325-333
A fluorescent converter for fast neutron radiography (FNR) comprising a scintillator and hydrogen-rich resin has been developed and applied to electronic imaging. The rate of the reaction between fast neutrons and the converter is increased by thickening the converter, but its opaqueness attenuates emitted light photons before they reach its surface. To improve the luminosity of a fluorescent converter for FNR, a novel type of converter was designed in which wavelength-shifting fibers were adopted to transport radiated light to the observation end face. The performance of the converter was compared with that of a polypropylene-based fluorescent converter in an experiment conducted at the fast-neutron-source reactor YAYOI in the University of Tokyo. 相似文献
34.
Spruce wood residues were treated in a vacuum pyrolysis Process Development Unit with a throughput capacity of 28 kg/h. Two aqueous phase condensate samples with COD concentration varying between 190 and 255 g/L were produced and sequentially extracted with dichloromethane and ethylacetate solvents. The soluble organic matter was composed of acidic, phenolic, alcoholic and ketonic compounds. The insoluble fraction was sequentially distilled at 100 and 110°C under atmospheric pressure. Mainly water was recovered in the first distillate, while the second distillate contained 30.4% formic and acetic acids, 69.4% water and 0.2% residual organic compounds. The distillation residue was rich in oxygen and was essentially insoluble in any organic solvent. The two aqueous phase pyroligneous samples were treated in Bat-telle's Thermochemical Environmental Energy System (TEESr?), a registered service mark of Onsite*Ofsite, Inc. of Duarte, California, U.S.A. The results of the tests showed that similar results were obtained with either feedstock. In batch tests a COD reduction of 99% was achieved. The product gas composition was typically about 49% methane, 5% hydrogen, 1 % ethane and 45% carbon dioxide. Tests in a continuous stirred-tank reactor produced reproducible data which can be used for process scale-up. Catalyst lifetime was identified as needing further improvement. The preliminary results demonstrated the technical feasibility of the catalytic gasification process as a useful step in the recovery of energy from the secondary condensate stream and the cleanup of the by-product water from vacuum pyrolysis of wood. 相似文献
35.
David A. Carlson 《The Journal of supercomputing》1992,6(2):107-116
In this paper a set of techniques for improving the performance of the fast Fourier transform (FFT) algorithm on modern vector-oriented supercomputers is presented. Single-processor FFT implementations based on these techniques are developed for the CRAY-2 and the CRAY Y-MP, and it is shown that they achieve higher performance than previously measured on these machines. The techniques include (1) using gather/scatter operations to maintain optimum length vectors throughout all stages of small-to medium-sized FFTs, (2) using efficient radix-8 and radix-16 inner loops, which allow a large number of vector loads/stores to be overlapped, and (3) prefetching twiddle factors as vectors so that on the CRAY-2 they can later be fetched from local memory in parallel with common memory accesses. Performance results for Fortran implementations using these techniques demonstrate that they are faster than Cray's library FFT routine CFFT2. The actual speedups obtained, which depend on the size of the FFT being computed and the supercomputer being used, range from about 5 to over 300%. 相似文献
36.
The effect of reducing the reactor air pressure on the morphology of spray dried magnesium sulphate powders is investigated, experimentally. A reactor, capable of drying and pyrolyzing solution sprays at low pressures, is designed and manufactured. A vibrating mesh nebulizer is employed to generate the spray. Four different pressures, starting from 60 Torr to the atmospheric pressure, and two different reactor air temperatures of 130°C and 420°C, are considered. In addition, two different concentrations of magnesium sulphate solutions are tested. The results are explained based on the effect of reactor air pressure on the droplet evaporation rate. 相似文献
37.
Alumina coatings have been deposited by combustion flame pyrolysis on amorphous silica and stainless steel substrates with the objective to study the effect of solvent composition, Fe3+ addition and determine the thermal fatigue lifetime. The effect of solvent composition on crystallinity, transformation temperature and hardness are studied, three different solvent compositions are chosen for preparing the aluminium nitrate solution. Using 100% water, as-deposited films are amorphous and transform to α-alumina only upon annealing, while this equilibrium phase is directly obtained but with a porous microstructure by using 100% methanol. The hardness of the coatings varies with the flammability of the solvents. The effect of Fe3+ addition on the crystallization of alumina is studied by combustion pyrolysis of aqueous solutions of Al3+ and Fe3+ nitrates. Small amount of ferric nitrate reduced the transformation temperature by 100 °C. Thermal cycling of as-deposited amorphous alumina on stainless steel substrate is carried out at different temperatures to determine the thermal fatigue lifetime. 相似文献
38.
Semiconducting molybdenum trioxide thin films have been prepared by employing simple and inexpensive spray pyrolysis technique.
Films are found to be polycrystalline in nature with hexagonal phase. Optical band gap energy (direct) and room temperature
electrical resistivity are of the order of 2·9 eV and 108 ohm-cm, respectively. These films exhibit cathodic electrochromism. 相似文献
39.
Fast pyrolysis of heavy metal contaminated birch (CMB), resulting from phytoremediation, is investigated. The effect of the pyrolysis temperature (673, 773, 873 K) on the composition and evolution of the bio-oil/tar fraction and the gas fraction has been studied. The knowledge of the composition of the gaseous and liquid pyrolysis fractions, as a function of the pyrolysis temperature, affects directly future applications and valorisation of the pyrolysis products and are indispensable for making and selecting the proper thermal conditions for their optimal use. In view of the future valorisation of this heavy metal contaminated biomass, the pyrolysis temperature is imperative, because some of the heavy metals can volatilize at temperatures generally used for the co-combustion or fast pyrolysis of biomass. 相似文献
40.